From what I have read, as long as I don't screw-up the RFID ring antenna around the front of the lock I will be OK. Replacing the tumbler involves turning the key to position 1 & inserting a special tool (coat hanger) into the lock assembly to release the tumbler catch & pulling out the old tumbler. Installation is just the opposite.

The manual has pretty good instructions for disassembling the dash to get at the switch, but I wish I could find section 8D.

I guess I will be blazing a trail here in the Crossfire community because from everything I have read this is a very common problem in just about everything MB makes (a search for "ignition tumbler" came back with 411 threads). I'll make sure I take lots of pictures and write up a DYI instruction sheet when I'm done.